1. Field of the Invention
The present invention relates to a control system and method of an internal combustion engine, and in particular, to one for improving self-diagnosis accuracy.
2. Description of the Related Art
Some internal combustion engines of vehicles or the like have a self-diagnosis system for executing a self-diagnosis process for examining provided components or elements such as catalysts, O2 sensors, evaporating fuel, and the like, so as to detect abnormal states, for example, degradation of relevant components. Generally, the determination of normal or abnormal conditions is performed when predetermined conditions are satisfied.
Japanese Unexamined Patent Application, First Publication, No. Hei 9-41952 discloses an example system of determining the degradation of a catalyst, in which such a self-diagnosis process is performed only when the temperature of the intake air, the temperature of cooling water, and the vehicle speed satisfy the conditions provided for the self-diagnosis. Therefore, the self-diagnosis is not executed when the conditions are not satisfied, for example, when the above-mentioned temperature of the intake air, the temperature of cooling water, and the vehicle speed deviate from corresponding predetermined ranges, or when a sudden load change occurs.
However, in the above conventional self-diagnosis system of internal combustion engines, even if a load change occurs which is not very large, that is, the degree thereof is smaller than a predetermined degree of a xe2x80x9csuddenxe2x80x9d load change, relevant observed values become unstable and the accuracy is degraded. Here, the predetermined degree of the sudden load change may be a 48 hPA variation in the air intake passage absolute pressure (xcex94PB).
If the threshold for the load change, that is, the allowable range for the predetermined condition of the self-diagnosis process is defined very strictly, the above degradation in accuracy can be prevented to a certain degree; however, the self-diagnosis is performed less often, and the frequency of stopping during execution increases.
In consideration of the above circumstances, an objective of the present invention is to provide a control system and method of an internal combustion engine for improving the self-diagnosis accuracy and decreasing the frequency of stopping the self-diagnosis process.
Therefore, the present invention provides a control system of an internal combustion engine (for example, engine 1 in FIGS. 1 and 9 in the embodiment explained below) in a vehicle, the control system being built into the vehicle, comprising:
a self-diagnosis section for executing self-diagnosis of the internal combustion engine (for example, executing step S1 in FIG. 2 and step S51 in FIG. 10 in the embodiment explained below);
a load control section (for example, motor 21, CVT 22, and VTC 23 in FIGS. 1 and 9, and electric actuator 24 in FIG. 1 in the embodiment explained below) for controlling a load imposed on the internal combustion engine; and
a normal driving control section (for example, ECU 5 in FIGS. 1 and 9 in the embodiment explained below) for maintaining a normal driving state in which a variation in the load imposed on the internal combustion engine is suppressed, by operating the load control section while the self-diagnosis is being executed by the self-diagnosis section and while the current driving state of the vehicle is in a predetermined driving range.
Accordingly, when the conditions for executing the self-diagnosis are satisfied, if a load change occurs which is not very large, that is, the degree thereof is smaller than a predetermined degree of the above-explained sudden load change, the normal driving state can be maintained by operating the load control section via the normal driving control section so as to suppress the load variation. Therefore, the self-diagnosis can be more often executed by the self-diagnosis section, and the accuracy of the self-diagnosis can be improved.
It is possible in the above structure that:
the vehicle has a throttle valve and an accelerator;
the load control section includes a throttle valve control section for performing electric drive control of the degree of opening of the throttle (for example, degree of throttle opening xcex8TH detected by sensor 4 in FIGS. 1 and 9 in the embodiment explained below) according to the degree of opening of the accelerator (for example, degree of accelerator opening xcex8Acc detected by device 26 in FIG. 1 in the embodiment explained below) and the driving state of the vehicle (for example, executing step S3 in FIG. 2 in the embodiment explained below); and
the normal driving control section suppresses a variation in the degree of opening of the throttle by operating the throttle valve control section.
In this case, when the conditions for executing the self-diagnosis are satisfied, if a load change in the internal combustion engine occurs, the normal driving control section can suppress a variation in the degree of throttle opening by using the throttle valve control section. Therefore, a variation in the air intake passage absolute pressure (PB) due to a variation in the degree of throttle opening can be suppressed; thus, the self-diagnosis can be more often executed by the self-diagnosis section, and the accuracy of the self-diagnosis can be improved.
It is also possible that:
the load control section includes a motor (for example, motor 21 in FIGS. 1 and 9 in the embodiment explained below) as a driving source of the vehicle and a hybrid control section for performing drive control of the motor according to the driving state of the vehicle (for example, executing step S7 in FIG. 2 and step S56 in FIG. 10 in the embodiment explained below); and
the normal driving control section maintains the normal driving state by operating the hybrid control section.
Accordingly, when the conditions for executing the self-diagnosis are satisfied, if a load change in the internal combustion engine occurs, the normal driving control section can suppress a variation in the load of the internal combustion engine by making the hybrid control section drive the motor. Therefore, the self-diagnosis can be more often executed by the self-diagnosis section, and the accuracy of the self-diagnosis can be improved.
The hybrid control section may control the amount of regeneration using the motor. Typically, the hybrid control section controls the amount of regeneration when it is determined that the driver of the vehicle intends to accelerate or decelerate.
The hybrid control section may control the amount of driving assistance using the motor. Typically, the hybrid control section controls the amount of driving assistance when it is determined that the driver of the vehicle intends to accelerate or decelerate.
The present invention also provides a control method of an internal combustion engine in a vehicle, comprising:
a self-diagnosis step of executing self-diagnosis of the internal combustion engine;
a load control step of controlling a load imposed on the internal combustion engine; and
a normal driving control step of maintaining a normal driving state in which a variation of the load imposed on the internal combustion engine is suppressed, by executing the load control step while the self-diagnosis is being executed in the self-diagnosis step and while the current driving state of the vehicle is in a predetermined driving range.
It is possible that:
the vehicle has a throttle valve and an accelerator;
the load control step includes a throttle valve control step of performing electric drive control of the degree of opening of the throttle according to the degree of opening of the accelerator and the driving state of the vehicle; and
in the load control step, a variation in the degree of opening of the throttle is suppressed by executing the throttle valve control step.
It is also possible that:
the vehicle has a motor as a driving source of the vehicle and the load control step includes a hybrid control step of performing drive control of the motor according to the driving state of the vehicle; and
in the normal driving control step, the normal driving state is maintained by executing the hybrid control step.
The hybrid control step may include controlling an amount of regeneration using the motor. Typically, the hybrid control step includes controlling the amount of regeneration when it is determined that the driver of the vehicle intends to accelerate or decelerate.
On the other hand, the hybrid control step may include controlling an amount of driving assistance using the motor. Typically, the hybrid control step includes controlling the amount of driving assistance when it is determined that the driver of the vehicle intends to accelerate or decelerate.
According to the above method, the effects described in the explanation for the control system can also be obtained.
The present invention also provides a computer readable storage medium storing a program for making a computer execute an operation of controlling an internal combustion engine in a vehicle, the operation comprising:
a self-diagnosis step of executing self-diagnosis of the internal combustion engine;
a load control step of controlling a load imposed on the internal combustion engine; and
a normal driving control step of maintaining a normal driving state in which a variation of the load imposed on the internal combustion engine is suppressed, by executing the load control step while the self-diagnosis is being executed in the self-diagnosis step and while the current driving state of the vehicle is in a predetermined driving range.